1. Field of the Invention
The present invention relates generally to an image sensor, and more particularly to an image sensor supporting a binning operation.
2. Description of the Related Art
Image sensors convert an optical image signal into an electrical image signal and are widely used in various electronic products such as mobile phones, personal computer cameras, video cameras, digital cameras, etc.
The image sensors support binning in a preview mode, a HD format mode, etc. in order to support requirements of the modern electronic products such as a high resolution, a small pixel size, a high frame speed, etc. Binning allows charges from adjacent pixels to be combined for faster readout speeds and improved signal to noise ratios although the spatial resolution may be reduced.
Certain binning operations may include: averaging the pixel signals from pixels by splitting the capacitors included in the correlated double sampling devices (CDSs) into two or four; or storing and summing pixel signals by adding extra capacitors to the CDSs.
In the case of splitting capacitors included in the CDSs, image improvement through the summation of pixel signals is not possible, since the capacitances of capacitors included in respective CDSs are identical. In the case of storing and summing pixels signals by adding extra capacitors, image improvement may be possible, but this increases the overall size of an image sensor due to an increase in the capacitances of capacitors, because the increased capacitances of capacitors included in respective CDSs.